Many pourable food products, such as fruit juice, UHT milk, wine, tomato sauce, etc., are sold in packages made of sterilized packaging material.
A typical example of such a package is the parallelepiped-shaped package for liquid or pourable food products known as Tetra Brik or Tetra Brik Aseptic (registered trademarks), which is formed by folding and sealing laminated strip packaging material. The packaging material has a multilayer structure comprising a layer of fibrous material, e.g. paper, covered on both sides with layers of heat-seal plastic material, e.g. polyethylene, and, in the case of aseptic packages for long-storage products, such as UHT milk, also comprises a layer of barrier material defined, for example, by an aluminium film, which is superimposed on a layer of heat-seal plastic material and is in turn covered with another layer of heat-seal plastic material eventually defining the inner face of the package contacting the food product.
As is known, such packages are made on fully automatic packaging units, on which a continuous tube is formed from the web-fed packaging material; the web of packaging material is sterilized on the packaging unit itself, e.g. by applying a chemical sterilizing agent, such as a hydrogen peroxide solution, which, after sterilization, is removed, e.g. vaporized by heating, from the surfaces of the packaging material; and the web of packaging material so sterilized is maintained in a closed sterile environment, and is folded and sealed longitudinally to form a vertical tube.
The tube is filled continuously from the top with the sterilized or sterile-processed food product, and is sealed and cut at equally spaced cross sections to form pillow packs, which are then folded mechanically to form the finished, e.g. substantially parallelepiped-shaped, packages.
Alternatively, the packaging material may be cut into blanks, which are formed into packages on forming spindles, and the resulting packages are filled with the food product and sealed. One example of such a package is the so-called “gable-top” package commonly known by the trade name Tetra Rex (registered trademark).
The above packages are normally provided with closable opening devices to permit consumption of, and prevent external agents from coming into contact with, the food product in the package.
The opening devices most commonly used at present comprise a frame defining an opening and fitted over a hole or a pierceable or removable portion in a top wall of the package; and a cap hinged or screwed to the frame and which is removable to open the package. Alternatively, other, e.g. slide-type, opening devices are also known to be used.
Regardless of the type of opening device used, the top wall of the package formed from the tube of packaging material has a number of sealing bands which limit the amount of space available in which to fit the opening device to the top wall. In particular, the top wall is crossed along the centerline by a flat transverse sealing band folded down onto and coplanar with the top wall; and by an end portion of a flat longitudinal sealing band extending perpendicularly from the transverse sealing band. More specifically, the longitudinal sealing band extends along a portion of the top wall of the package, and downwards from the top wall along a lateral wall and a bottom wall of the package.
Likewise, spindle-formed packages also comprise a top wall crossed along the centerline by a flat transverse sealing band folded down onto and coplanar with the top wall.
In neither case can the opening device be fitted to the sealing bands of the package, which would not only pose problems in sealing the device onto an uneven surface, but would also impair the integrity of the seals themselves.
The opening device can therefore only be fitted to the limited flat portions adjacent to the sealing bands extending across the top wall of the package, which obviously limits the maximum size of the opening device.
The above drawback is particularly felt in view of the increasing number of physically different products marketed in packages made of paperlike packaging material, some of which, particularly semiliquid products or products containing fibers or particles, require a larger opening device for the product to be poured smoothly.
To increase the space in which to fit the opening device to the package, it has been proposed to invert the direction in which the transverse sealing band is folded onto the top wall, by folding it onto the longitudinal sealing band side. The amount of extra space gained this way, however, has been relatively small.
Another proposed solution is to provide the front edge of the top wall of the package with a convex C-shaped bend line or so-called “smile crease” formed beforehand on the packaging material and projecting outwards of the package.
This solution provides for obtaining more space for the opening device than by inverting the folding direction of the transverse sealing band. Nevertheless, a demand exists in the industry for further improvement, particularly as regards research into new solutions enabling further increase in the space available on the package for even larger opening devices.